I'd go with 10gb devoted to Linux for right now. Meaning:
1.) Resize (using ParititonMagic) your Windows drive to whatever it's at minus 10240MB. You can do this by right-clicking on the partition in PartitionMagic, selecting Resize/Move, and in the "Space After" box, specifying 10240.00mb. (Megabytes should be the default unit in the dialog).
2.) Create a new FAT32 partition using PartitionMagic (this partition will be accessible to both installations for read-write mode). Make it a moderate size, but not very big; 256mb or even 512mb should be plenty of room. Make backup floppies the way PartitionMagic lets you.
3.) Tell PartitionMagic to apply these changes. You will have to reboot, and ParititonMagic will do its work before Windows boots (the same place it would run chkdsk on startup). This will take quite a while, because if there's any data on the end of your disk (there is), it needs to be moved closer to the front of the disk to make room for the new space. I suggest leaving this to happen overnight, or doing something constructive in the meantime, like playing
Elder Scrolls IV: Oblivion (which is for Windows or Xbox 360, as it turns out -- not Linux
).
4.) Once you've done this, verify that the changes have been performed, then reboot with the Fedora Core CD 1 in the drive (I was pissed that it wasn't a DVD image). Anaconda, the FC5 installer program, will load and walk you through the installation. There are a lot of features if you do a custom install -- it's pretty thorough. I suggest you stick with GNOME as your window manager and go from there.
I just got it installed on my laptop, a painfully slow 2 hour process (of course I added a lot of packages, like NmapFE (yes I know iago, using a GUI for Nmap is like blasphemy) and the spread of the CD usage was not consistent), but all told it did well. Despite the claim to support Broadcom WiFi cards, unfortunately it does not have drivers for mine, so I need to hunt down instructions for compiling NDISWrapper for FC5. However, it did detect my sound card this time, as opposed to last time, when it just crashed my notebook.
It looks good, runs faster than before.